// GenericsNote: Converted.
/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections15;

import java.util.Iterator;

/**
 * Defines an iterator that operates over a <code>Map</code>.
 * <p/>
 * This iterator is a special version designed for maps. It can be more
 * efficient to use this rather than an entry set iterator where the option is
 * available, and it is certainly more convenient.
 * <p/>
 * A map that provides this interface may not hold the data internally using Map
 * Entry objects, thus this interface can avoid lots of object creation.
 * <p/>
 * In use, this iterator iterates through the keys in the map. After each call
 * to <code>next()</code>, the <code>getValue()</code> method provides direct
 * access to the value. The value can also be set using <code>setValue()</code>.
 * 
 * <pre>
 * MapIterator it = map.mapIterator();
 * while (it.hasNext()) {
 * 	Object key = it.next();
 * 	Object value = it.getValue();
 * 	it.setValue(newValue);
 * }
 * </pre>
 *
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:19 $
 * @since Commons Collections 3.0
 */
public interface MapIterator<K, V> extends Iterator<K> {

	/**
	 * Checks to see if there are more entries still to be iterated.
	 *
	 * @return <code>true</code> if the iterator has more elements
	 */
	@Override
	boolean hasNext();

	/**
	 * Gets the next <em>key</em> from the <code>Map</code>.
	 *
	 * @return the next key in the iteration
	 * @throws java.util.NoSuchElementException
	 *             if the iteration is finished
	 */
	@Override
	K next();

	// -----------------------------------------------------------------------
	/**
	 * Gets the current key, which is the key returned by the last call to
	 * <code>next()</code>.
	 *
	 * @return the current key
	 * @throws IllegalStateException
	 *             if <code>next()</code> has not yet been called
	 */
	K getKey();

	/**
	 * Gets the current value, which is the value associated with the last key
	 * returned by <code>next()</code>.
	 *
	 * @return the current value
	 * @throws IllegalStateException
	 *             if <code>next()</code> has not yet been called
	 */
	V getValue();

	// -----------------------------------------------------------------------
	/**
	 * Removes the last returned key from the underlying <code>Map</code>
	 * (optional operation).
	 * <p/>
	 * This method can be called once per call to <code>next()</code>.
	 *
	 * @throws UnsupportedOperationException
	 *             if remove is not supported by the map
	 * @throws IllegalStateException
	 *             if <code>next()</code> has not yet been called
	 * @throws IllegalStateException
	 *             if <code>remove()</code> has already been called since the
	 *             last call to <code>next()</code>
	 */
	@Override
	void remove();

	/**
	 * Sets the value associated with the current key (optional operation).
	 *
	 * @param value
	 *            the new value
	 * @return the previous value
	 * @throws UnsupportedOperationException
	 *             if setValue is not supported by the map
	 * @throws IllegalStateException
	 *             if <code>next()</code> has not yet been called
	 * @throws IllegalStateException
	 *             if <code>remove()</code> has been called since the last call
	 *             to <code>next()</code>
	 */
	V setValue(V value);

}
